Piston and cylinder assembly



Dec. l2, 1933f M. BIRKIGT yPISTON AND CYLINDER ASSEMBLY Filed July 15 19:27`

Patented 12, 1933 UNITED STATES 1,988,530 PISTON AND CYLINDER ASSEMBL'Y- Marc Birkigt, Boil Colombes,

Application July 15, 192'?, Serial No. 206,114, and

in Be li` Claims. '(Cl. 30S-r3? The present invention relates to piston and cylinder assemblies and more Jparticularly to lthose adapted for use in internal combustion engines. v

One of the objects ofthe invention is to p rovidev an assembly capable of withstanding long use without appreciable wear of the surfaces in frictional contact.

Further objects will appear in the course of the detailed description which will now be given with reference to the single figure of the accompanying drawing which shows a section through `a.

` cylinder and piston assembly constructed in accordance with the invention.

a is a cylindrical shell formed with proper reenforcing ribs and mounted inside a shell a. `Shells w and a' denne a chamber az capable of receiving a cooling fluid. Cylinder a` is, preferably made of steel or similar nitridable material and zo has an internal surface which lhas been superilcially hardened by treatment with a nitrogenliberating material.. The piston sliding in contact with cylinder a is, preferably, made in two parts; i. e., an upper non-frictional partV b of aluminium, duralumin or similar light metal having annular piston ring recesses b1 (the piston rings themselves are not shown) formed therein, and a skirt portion c, preferably of steel which has been surface hardened in the same or in a similar manner to cylinder a. It will be noted that skirt c has an external diameter corresponding to that of the cylinder only at each extremity and that the intermediate portions are of lesser diameter, so as to diminish the wear lto a minimum.

As illustrated Yin the figure of the drawing, the head b has a reduced portion bl which nts snugly and telescopically within the skirt c. The upper part of the skirt c is flaredJ somewhat, as at c1, thereby forming with b2 an annular chamber cl opening outwardly through an annular aperture c4. Apertures cs provide communication between the annular chamber c and the interlor d of the piston.

In proceeding to construct the assembly above described, it is well to start with steel forsinss or the like corresponding in form to the cylinder and the piston skirt and to machine each of the latter to a proper ilt. The cylinder and the skirt may then be surface-hardened and' then reiinished to final working dimensions. Aluminium head b may be telescopically fitted into the skirt in the manner shown in the drawing or may be rigidly attached thereto in any other manner deaired.

In operation it is found'that the combination of two surface-hardened frictional surfaces reduces the frictional loss, permits high speed operation, reduces lubrication and wear, and, since metals of equal coefilcient of expansion 60 are used, minimizes piston s1ap.

The present invention, in certainof its broader phases, as above indicated, includes in a piston andrcylinder assembly the combination of two mutually contacting friction surfaces vof which either one or both have a thin, hard, wearresisting case or skin backed by softer metal, which skin is formed of ferrous metal that has been treated upon the wearing surface to incorporate with the metal thereof to an appreciable and effective depth nitrogen in the form of nitrides according to known nitriding processes, and particularly according to `the process described in U. S. Patent No. 1,487,554.

What I claim is:-

1. In an internal combustion engine, a cylinder having a hardened wearing surface portion containing nitroge'n in the nitride form.

2. In an internal combustion engine, a cylinder and a piston, having surface-hardened, mutually contacting` friction surfaces containing nitrogen in nitride form.

3. In an internal combustion engine, a cylinder .having a surface-hardened, wear-resisting ferrous metal surface such as may be produced tion temperature of said metal.

6. A piston and cylinder assembly for an internal combustion engine having surfacehardened mutually contacting, wear-resisting ferrous metal surfaces such as may be produced by heating such surfaces in the presence of nascent nitrogen at about the peritectoidal transformation temperature of said metal.

MARC BIRKIGT. 

